prepjointree.c

来自「postgresql8.3.4源码,开源数据库」· C语言 代码 · 共 1,329 行 · 第 1/3 页

	 * And now add any subquery InClauseInfos and AppendRelInfos to our lists.
	 */
	root->in_info_list = list_concat(root->in_info_list,
									 subroot->in_info_list);
	root->append_rel_list = list_concat(root->append_rel_list,
										subroot->append_rel_list);

	/*
	 * We don't have to do the equivalent bookkeeping for outer-join info,
	 * because that hasn't been set up yet.
	 */
	Assert(root->oj_info_list == NIL);
	Assert(subroot->oj_info_list == NIL);

	/*
	 * Miscellaneous housekeeping.
	 */
	parse->hasSubLinks |= subquery->hasSubLinks;
	/* subquery won't be pulled up if it hasAggs, so no work there */

	/*
	 * Return the adjusted subquery jointree to replace the RangeTblRef entry
	 * in parent's jointree.
	 */
	return (Node *) subquery->jointree;
}

/*
 * pull_up_simple_union_all
 *		Pull up a single simple UNION ALL subquery.
 *
 * jtnode is a RangeTblRef that has been identified as a simple UNION ALL
 * subquery by pull_up_subqueries.	We pull up the leaf subqueries and
 * build an "append relation" for the union set.  The result value is just
 * jtnode, since we don't actually need to change the query jointree.
 */
static Node *
pull_up_simple_union_all(PlannerInfo *root, Node *jtnode, RangeTblEntry *rte)
{
	int			varno = ((RangeTblRef *) jtnode)->rtindex;
	Query	   *subquery = rte->subquery;
	int			rtoffset;
	List	   *rtable;

	/*
	 * Append the subquery rtable entries to upper query.
	 */
	rtoffset = list_length(root->parse->rtable);

	/*
	 * Append child RTEs to parent rtable.
	 *
	 * Upper-level vars in subquery are now one level closer to their
	 * parent than before.	We don't have to worry about offsetting
	 * varnos, though, because any such vars must refer to stuff above the
	 * level of the query we are pulling into.
	 */
	rtable = copyObject(subquery->rtable);
	IncrementVarSublevelsUp_rtable(rtable, -1, 1);
	root->parse->rtable = list_concat(root->parse->rtable, rtable);

	/*
	 * Recursively scan the subquery's setOperations tree and add
	 * AppendRelInfo nodes for leaf subqueries to the parent's
	 * append_rel_list.
	 */
	Assert(subquery->setOperations);
	pull_up_union_leaf_queries(subquery->setOperations, root, varno, subquery,
							   rtoffset);

	/*
	 * Mark the parent as an append relation.
	 */
	rte->inh = true;

	return jtnode;
}

/*
 * pull_up_union_leaf_queries -- recursive guts of pull_up_simple_union_all
 *
 * Note that setOpQuery is the Query containing the setOp node, whose rtable
 * is where to look up the RTE if setOp is a RangeTblRef.  This is *not* the
 * same as root->parse, which is the top-level Query we are pulling up into.
 *
 * parentRTindex is the appendrel parent's index in root->parse->rtable.
 *
 * The child RTEs have already been copied to the parent. childRToffset
 * tells us where in the parent's range table they were copied.
 */
static void
pull_up_union_leaf_queries(Node *setOp, PlannerInfo *root, int parentRTindex,
						   Query *setOpQuery, int childRToffset)
{
	if (IsA(setOp, RangeTblRef))
	{
		RangeTblRef *rtr = (RangeTblRef *) setOp;
		int			childRTindex;
		AppendRelInfo *appinfo;

		/*
		 * Calculate the index in the parent's range table
		 */
		childRTindex = childRToffset + rtr->rtindex;

		/*
		 * Build a suitable AppendRelInfo, and attach to parent's list.
		 */
		appinfo = makeNode(AppendRelInfo);
		appinfo->parent_relid = parentRTindex;
		appinfo->child_relid = childRTindex;
		appinfo->parent_reltype = InvalidOid;
		appinfo->child_reltype = InvalidOid;
		make_setop_translation_lists(setOpQuery, childRTindex,
									 &appinfo->col_mappings,
									 &appinfo->translated_vars);
		appinfo->parent_reloid = InvalidOid;
		root->append_rel_list = lappend(root->append_rel_list, appinfo);

		/*
		 * Recursively apply pull_up_subqueries to the new child RTE.  (We
		 * must build the AppendRelInfo first, because this will modify it.)
		 * Note that we can pass below_outer_join = false even if we're
		 * actually under an outer join, because the child's expressions
		 * aren't going to propagate up above the join.
		 */
		rtr = makeNode(RangeTblRef);
		rtr->rtindex = childRTindex;
		(void) pull_up_subqueries(root, (Node *) rtr, false, true);
	}
	else if (IsA(setOp, SetOperationStmt))
	{
		SetOperationStmt *op = (SetOperationStmt *) setOp;

		/* Recurse to reach leaf queries */
		pull_up_union_leaf_queries(op->larg, root, parentRTindex, setOpQuery,
								   childRToffset);
		pull_up_union_leaf_queries(op->rarg, root, parentRTindex, setOpQuery,
								   childRToffset);
	}
	else
	{
		elog(ERROR, "unrecognized node type: %d",
			 (int) nodeTag(setOp));
	}
}

/*
 * make_setop_translation_lists
 *	  Build the lists of translations from parent Vars to child Vars for
 *	  a UNION ALL member.  We need both a column number mapping list
 *	  and a list of Vars representing the child columns.
 */
static void
make_setop_translation_lists(Query *query,
							 Index newvarno,
							 List **col_mappings, List **translated_vars)
{
	List	   *numbers = NIL;
	List	   *vars = NIL;
	ListCell   *l;

	foreach(l, query->targetList)
	{
		TargetEntry *tle = (TargetEntry *) lfirst(l);

		if (tle->resjunk)
			continue;

		numbers = lappend_int(numbers, tle->resno);
		vars = lappend(vars, makeVar(newvarno,
									 tle->resno,
									 exprType((Node *) tle->expr),
									 exprTypmod((Node *) tle->expr),
									 0));
	}

	*col_mappings = numbers;
	*translated_vars = vars;
}

/*
 * is_simple_subquery
 *	  Check a subquery in the range table to see if it's simple enough
 *	  to pull up into the parent query.
 */
static bool
is_simple_subquery(Query *subquery)
{
	/*
	 * Let's just make sure it's a valid subselect ...
	 */
	if (!IsA(subquery, Query) ||
		subquery->commandType != CMD_SELECT ||
		subquery->utilityStmt != NULL ||
		subquery->intoClause != NULL)
		elog(ERROR, "subquery is bogus");

	/*
	 * Can't currently pull up a query with setops (unless it's simple UNION
	 * ALL, which is handled by a different code path). Maybe after querytree
	 * redesign...
	 */
	if (subquery->setOperations)
		return false;

	/*
	 * Can't pull up a subquery involving grouping, aggregation, sorting, or
	 * limiting.
	 */
	if (subquery->hasAggs ||
		subquery->groupClause ||
		subquery->havingQual ||
		subquery->sortClause ||
		subquery->distinctClause ||
		subquery->limitOffset ||
		subquery->limitCount)
		return false;

	/*
	 * Don't pull up a subquery that has any set-returning functions in its
	 * targetlist.	Otherwise we might well wind up inserting set-returning
	 * functions into places where they mustn't go, such as quals of higher
	 * queries.
	 */
	if (expression_returns_set((Node *) subquery->targetList))
		return false;

	/*
	 * Don't pull up a subquery that has any volatile functions in its
	 * targetlist.	Otherwise we might introduce multiple evaluations of these
	 * functions, if they get copied to multiple places in the upper query,
	 * leading to surprising results.
	 */
	if (contain_volatile_functions((Node *) subquery->targetList))
		return false;

	/*
	 * Hack: don't try to pull up a subquery with an empty jointree.
	 * query_planner() will correctly generate a Result plan for a jointree
	 * that's totally empty, but I don't think the right things happen if an
	 * empty FromExpr appears lower down in a jointree. Not worth working hard
	 * on this, just to collapse SubqueryScan/Result into Result...
	 */
	if (subquery->jointree->fromlist == NIL)
		return false;

	return true;
}

/*
 * is_simple_union_all
 *	  Check a subquery to see if it's a simple UNION ALL.
 *
 * We require all the setops to be UNION ALL (no mixing) and there can't be
 * any datatype coercions involved, ie, all the leaf queries must emit the
 * same datatypes.
 */
static bool
is_simple_union_all(Query *subquery)
{
	SetOperationStmt *topop;

	/* Let's just make sure it's a valid subselect ... */
	if (!IsA(subquery, Query) ||
		subquery->commandType != CMD_SELECT ||
		subquery->utilityStmt != NULL ||
		subquery->intoClause != NULL)
		elog(ERROR, "subquery is bogus");

	/* Is it a set-operation query at all? */
	topop = (SetOperationStmt *) subquery->setOperations;
	if (!topop)
		return false;
	Assert(IsA(topop, SetOperationStmt));

	/* Can't handle ORDER BY, LIMIT/OFFSET, or locking */
	if (subquery->sortClause ||
		subquery->limitOffset ||
		subquery->limitCount ||
		subquery->rowMarks)
		return false;

	/* Recursively check the tree of set operations */
	return is_simple_union_all_recurse((Node *) topop, subquery,
									   topop->colTypes);
}

static bool
is_simple_union_all_recurse(Node *setOp, Query *setOpQuery, List *colTypes)
{
	if (IsA(setOp, RangeTblRef))
	{
		RangeTblRef *rtr = (RangeTblRef *) setOp;
		RangeTblEntry *rte = rt_fetch(rtr->rtindex, setOpQuery->rtable);
		Query	   *subquery = rte->subquery;

		Assert(subquery != NULL);

		/* Leaf nodes are OK if they match the toplevel column types */
		/* We don't have to compare typmods here */
		return tlist_same_datatypes(subquery->targetList, colTypes, true);
	}
	else if (IsA(setOp, SetOperationStmt))
	{
		SetOperationStmt *op = (SetOperationStmt *) setOp;

		/* Must be UNION ALL */
		if (op->op != SETOP_UNION || !op->all)
			return false;

		/* Recurse to check inputs */
		return is_simple_union_all_recurse(op->larg, setOpQuery, colTypes) &&
			is_simple_union_all_recurse(op->rarg, setOpQuery, colTypes);
	}
	else
	{
		elog(ERROR, "unrecognized node type: %d",
			 (int) nodeTag(setOp));
		return false;			/* keep compiler quiet */
	}
}

/*
 * has_nullable_targetlist
 *	  Check a subquery in the range table to see if all the non-junk
 *	  targetlist items are simple variables or strict functions of simple
 *	  variables (and, hence, will correctly go to NULL when examined above
 *	  the point of an outer join).
 *
 * NOTE: it would be correct (and useful) to ignore output columns that aren't
 * actually referenced by the enclosing query ... but we do not have that
 * information available at this point.
 */
static bool
has_nullable_targetlist(Query *subquery)
{
	ListCell   *l;

	foreach(l, subquery->targetList)
	{
		TargetEntry *tle = (TargetEntry *) lfirst(l);

		/* ignore resjunk columns */
		if (tle->resjunk)
			continue;

		/* Must contain a Var of current level */
		if (!contain_vars_of_level((Node *) tle->expr, 0))
			return false;

		/* Must not contain any non-strict constructs */
		if (contain_nonstrict_functions((Node *) tle->expr))
			return false;

		/* This one's OK, keep scanning */
	}
	return true;
}

/*
 * is_safe_append_member
 *	  Check a subquery that is a leaf of a UNION ALL appendrel to see if it's
 *	  safe to pull up.
 */
static bool
is_safe_append_member(Query *subquery)
{
	FromExpr   *jtnode;
	ListCell   *l;

	/*
	 * It's only safe to pull up the child if its jointree contains exactly
	 * one RTE, else the AppendRelInfo data structure breaks. The one base RTE
	 * could be buried in several levels of FromExpr, however.
	 *
	 * Also, the child can't have any WHERE quals because there's no place to
	 * put them in an appendrel.  (This is a bit annoying...) If we didn't
	 * need to check this, we'd just test whether get_relids_in_jointree()
	 * yields a singleton set, to be more consistent with the coding of
	 * fix_append_rel_relids().
	 */
	jtnode = subquery->jointree;
	while (IsA(jtnode, FromExpr))
	{
		if (jtnode->quals != NULL)
			return false;
		if (list_length(jtnode->fromlist) != 1)
			return false;
		jtnode = linitial(jtnode->fromlist);
	}
	if (!IsA(jtnode, RangeTblRef))
		return false;

	/*
	 * XXX For the moment we also have to insist that the subquery's tlist
	 * includes only simple Vars.  This is pretty annoying, but fixing it
	 * seems to require nontrivial changes --- mainly because joinrel tlists
	 * are presently assumed to contain only Vars.	Perhaps a pseudo-variable
	 * mechanism similar to the one speculated about in pull_up_subqueries'
	 * comments would help?  FIXME someday.
	 */
	foreach(l, subquery->targetList)
	{
		TargetEntry *tle = (TargetEntry *) lfirst(l);

		if (tle->resjunk)
			continue;
		if (!(tle->expr && IsA(tle->expr, Var)))
			return false;
	}

	return true;
}

/*
 * Helper routine for pull_up_subqueries: do ResolveNew on every expression
 * in the jointree, without changing the jointree structure itself.  Ugly,
 * but there's no other way...
 */
static void
resolvenew_in_jointree(Node *jtnode, int varno,
					   RangeTblEntry *rte, List *subtlist)
{
	if (jtnode == NULL)
		return;
	if (IsA(jtnode, RangeTblRef))
	{
		/* nothing to do here */
	}
	else if (IsA(jtnode, FromExpr))
	{
		FromExpr   *f = (FromExpr *) jtnode;
		ListCell   *l;

		foreach(l, f->fromlist)
			resolvenew_in_jointree(lfirst(l), varno, rte, subtlist);
		f->quals = ResolveNew(f->quals,
							  varno, 0, rte,
							  subtlist, CMD_SELECT, 0);
	}
	else if (IsA(jtnode, JoinExpr))
	{